The Optimization of Lamb and Rayleigh Wave Generation Using Wideband-Low-Frequency EMATs

2003 ◽  
Author(s):  
S. Dixon
Keyword(s):  
Rayleigh Wave ◽  
Low Frequency ◽  
Wave Generation

Methods to isolate retrograde and prograde Rayleigh-wave signals

2019 ◽  
Vol 219 (2) ◽  
pp. 975-994 ◽  
Author(s):  
Gabriel Gribler ◽  
T Dylan Mikesell
Keyword(s):  
Rayleigh Wave ◽  
Time Domain ◽  
Fundamental Mode ◽  
Poisson Ratio ◽  
Low Frequency ◽  
Wave Dispersion ◽  
Low Frequencies ◽  
Retrograde Motion ◽  
Mode Identification ◽  
Time Frequency

SUMMARY Estimating shear wave velocity with depth from Rayleigh-wave dispersion data is limited by the accuracy of fundamental and higher mode identification and characterization. In many cases, the fundamental mode signal propagates exclusively in retrograde motion, while higher modes propagate in prograde motion. It has previously been shown that differences in particle motion can be identified with multicomponent recordings and used to separate prograde from retrograde signals. Here we explore the domain of existence of prograde motion of the fundamental mode, arising from a combination of two conditions: (1) a shallow, high-impedance contrast and (2) a high Poisson ratio material. We present solutions to isolate fundamental and higher mode signals using multicomponent recordings. Previously, a time-domain polarity mute was used with limited success due to the overlap in the time domain of fundamental and higher mode signals at low frequencies. We present several new approaches to overcome this low-frequency obstacle, all of which utilize the different particle motions of retrograde and prograde signals. First, the Hilbert transform is used to phase shift one component by 90° prior to summation or subtraction of the other component. This enhances either retrograde or prograde motion and can increase the mode amplitude. Secondly, we present a new time–frequency domain polarity mute to separate retrograde and prograde signals. We demonstrate these methods with synthetic and field data to highlight the improvements to dispersion images and the resulting dispersion curve extraction.

scholarly journals Review on the Millimeter-Wave Generation Techniques Based on Photon Assisted for the RoF Network System

2020 ◽  
Vol 2020 ◽  
pp. 1-14
Author(s):  
Jiangnan Xiao ◽  
Chuang Zhao ◽  
Xingxing Feng ◽  
Xu Dong ◽  
Jiangli Zuo ◽  
...  
Keyword(s):  
High Frequency ◽  
Low Cost ◽  
Electronic Devices ◽  
Low Frequency ◽  
Digital Signal ◽  
Development Trend ◽  
Wave Generation ◽  
Communication Link ◽  
Network System ◽  
High Frequency Microwave

With the development trend of wireless and broadband in the communication link and even the whole information industry, the demand of high-frequency microwave bandwidth has been increasing. The RoF network system solves the problem of spectrum congestion in low-frequency band by providing an effective technology for the distribution of high-frequency microwave signals over optical fiber links. However, the traditional mm-wave generation technique is limited by the bandwidth of electronic devices. It is difficult to generate high-frequency and low-phase noise mm-wave signals with pure electrical components. The mm-wave communication technology based on photon assisted can overcome the bandwidth bottleneck of electronic devices and provide the potential for developing the low-cost infrastructure demand of broadband mobile services. This paper will briefly explain the characteristics of the RoF network system and the advantages of high-frequency mm-wave. Then we, respectively, introduce the modulation schemes of RoF mm-wave generation based on photon assisted including directly modulated laser (DML), external modulation, and optical heterodyne. The review mainly focuses on a variety of different mm-wave generation technologies including multifrequency vector mm-wave. Furthermore, we list several approaches to realize the large capacity data transmission techniques and describe the digital signal processing (DSP) algorithm flow in the receiver. In the end, we summarize the RoF network system and look forward to the future.

An analytical study on the Rayleigh wave generation in a stratified structure

2020 ◽  
Vol 41 (7) ◽  
pp. 1039-1054
Author(s):  
A. Mandi ◽  
S. Kundu ◽  
P. Pati ◽  
P. C. Pal
Keyword(s):  
Rayleigh Wave ◽  
Analytical Study ◽  
Wave Generation ◽  
Stratified Structure

Combination of Active and Passive Seismic Analyses for Embankment Characterization

2015 ◽  
Vol 771 ◽  
pp. 179-182 ◽  
Author(s):  
Yekti Widyaningrum ◽  
Sungkono ◽  
Alwi Husein ◽  
Bagus Jaya Santosa ◽  
Ayi S. Bahri
Keyword(s):  
Rayleigh Wave ◽  
High Frequency ◽  
Low Frequency ◽  
Wave Dispersion ◽  
Standard Penetration Test ◽  
Near Surface ◽  
Combining Data ◽  
Passive Seismic ◽  
Estimate Dispersion ◽  
Rayleigh Wave Dispersion

Rayleigh wave dispersion is intensively used to determine near surface of shear wave velocity (Vs). The method has been known as non-invasive techniques which is costly effective and efficient to characterize subsurface. Acquisition of the Rayleigh wave can be approached in two ways, i.e. passive and active. Passive seismic is accurate to estimate dispersion curve in low frequency, although it is not accurate for high frequency. While active seismic is vice versa of passive seismic. The high frequency of Rayleigh wave dispersion reflects to near surface and vice versa. Therefore, we used the combination of both passive and active seismic method to overcome the limitations of each method. The Vs which is resulted by inversion of the combining data gives accurate model if compared to log and standard penetration test (N-SPT) data. Further, the approach has been used to characterize LUSI (Lumpur Sidoarjo) embankments. The result shows that embankment material (0-12 m) has higher Vs than that lower embankment material.

Researching on Characteristics of Rayleigh Waves

2014 ◽  
Vol 721 ◽  
pp. 472-475
Author(s):  
Xu Fang Zhu ◽  
Bing Yan
Keyword(s):  
Wave Equation ◽  
Rayleigh Wave ◽  
Dispersion Equation ◽  
Rayleigh Waves ◽  
Low Frequency ◽  
Secondary Wave ◽  
Reflected Wave ◽  
Strong Energy ◽  
Geological Information ◽  
Interface Distance

Rayleigh wave is a secondary wave characterized by low frequency and strong energy, propagating mainly along the interface of medium and rapid attenuation of energy with increase in interface distance. The same as reflected wave and refracted wave, Rayleigh wave also contain subsurface geological information. In this paper, the concept of the Rayleigh wave, wave equation, dispersion equation, the frequency bulk characteristics and the application of the actual data are used to indicate the characteristics of Rayleigh wave and its application.

Observation of low‐frequency wave generation in a bubble layer.

1996 ◽  
Vol 99 (4) ◽  
pp. 2573-2574
Author(s):  
Alexander M. Sutin ◽  
Irina A. Soustova ◽  
Alexander I. Matveyev ◽  
Andrey I. Potapov ◽  
Lev. A. Ostrovsky
Keyword(s):  
Low Frequency ◽  
Wave Generation ◽  
Frequency Wave ◽  
Bubble Layer

Anomalous surface waves from underground explosions

1979 ◽  
Vol 69 (6) ◽  
pp. 1995-2002 ◽  
Author(s):  
Eivind Rygg
Keyword(s):  
Rayleigh Wave ◽  
Surface Waves ◽  
Rayleigh Waves ◽  
Major Part ◽  
Wave Generation ◽  
Love Waves ◽  
Phase Reversal ◽  
Wave Phase ◽  
Anomalous Surface

abstract The Rayleigh waves at Δ ∼40° from an eastern Kazakh explosion are shown to be polarity reversed and delayed relative to the Rayleigh waves from two other explosions of comparable magnitudes in the same area. The event generating the anomalous Rayleigh waves excited very strong Love waves which were not delayed. The Rayleigh wave phase reversal is shown to be a source phenomenon and it is suggested that in this particular case, spall closure was responsible for a major part of the Rayleigh-wave generation.

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